This revised application pertains to the newly implemented Health Behavior Module at the Center for Education and Drug Abuse Research (CEDAR). It is well established that risky sex (defined herein as unprotected vaginal or anal intercourse with a non-monogamous partner of uncertain risk) covaries with substance use during adolescence and young adulthood. Based on initial analyses conducted on the CEDAR sample, HAR and LAR youth differ strongly and at a comparatively young age with respect to risky sex. Because risky sex increases in incidence with drug involvement, the combined cumulative effect of these two domains of behavior needs to be determined with respect to the momentum and pathways to SUD between the critical transitions from adolescence to young adulthood. This Module aims to elucidate the relationship between substance use and risky sex in high-average risk (HAR) compared to low-average risk (LAR) adolescents. The global and event-specific associations, developmental patterning, and influence of risky sex, in predicting SUD and ATOD topography in young adulthood will be determined. Developmental and event-specific explanatory mechanisms will also be examined. CEDAR, a 20-year prospective investigation of 1,000 families, is presently completing its second period of funding. The groups of families are ascertained on the basis of a proband father who has a Substance Use Disorder (SUD), (High Average Risk, HAR, N=450), a non-SUD Axis I Psychiatric Disorder (Psychiatric Comparison; N= 100), as well as no other Axis I Psychiatric Disorder (Low Average Group, LAR, N=350). A non-contact group is also recruited (N=100) and followed-up after 20 years to determine whether participating in the study constituted an intervention (see Scientific and Clinical cores for additional details of the samples and recruitment strategies). Each family had a biological son or daughter (index subject) who is between 10-12 years of age at baseline assessment. Following baseline evaluation, the index subject, and where present, the next younger sibling are studied over a 20-year period until they attain age 30. In the course of the study the children are tracked from the stage of no drug use, to drug use, and to SUD. The other siblings, are also characterized with respect to psychiatric, psychosocial functioning, and sexual behavior. The determinants and characteristics of person- environment interactions that contribute to SUD liability and risky sex among index cases and siblings will thus be determined. From such information, empirically based selective preventions can be developed to target specific components of SUD liability.